What it means
Preventive maintenance is planned to reduce unplanned failures, and a service may be moved because a machine cannot stop, parts have not arrived or qualified staff are unavailable. A reschedule backlog shows planned jobs repeatedly deferred or past the new due date.
IBM describes preventive-maintenance schedules that generate recurring work orders based on time, meter usage or both, so the original due point is important evidence. Define reschedule carefully, because a corrected data-entry date is different from a real change to a planned maintenance window, and the reason and approval for each genuine move should be recorded.
Preserve the original due date: if a job first due September 1 moves to September 10 and then September 20, the current date alone hides how long it has waited. Choose the backlog population too, either all open preventive work orders with a rescheduled due date or only those now past the allowed maintenance window, and state which definition is used.
Check asset criticality, since delaying a safety-critical inspection and moving a low-risk cleaning task are not equivalent, so rank review by consequence, not just days. Measure age: an illustrative delay is revised planned completion September 20 minus original due September 1, or 19 calendar days, which is schedule movement and not proof the asset was unsafe for 19 days.
Count repeated moves as well, since a task shifted three times deserves closer scrutiny than one moved once for a planned shutdown, so record each event and not only the final date. A maintenance programme may define a tolerance around due time or meter reading, so interpret overdue status using its actual rule, and watch meter-based schedules because an asset with heavy use can become due sooner than the calendar forecast.
Record reasons, because production conflict, missing part, labour shortage, access restriction and vendor delay suggest different remedies and an "other" bucket should not hide a persistent cause. Connect parts availability and coordinate with operations: a job cannot begin if reserved components are not on site, and maintenance and production should agree on the next realistic window rather than repeatedly moving a provisional date.
Review legal or warranty obligations, since some inspections or service intervals have mandatory requirements and an internal schedule change does not waive those duties. Do not call a cancelled job completed, because a cancelled duplicate work order may be removed from backlog but the underlying maintenance requirement still needs a valid plan, and show open work and completed late work separately so that an improving closure rate does not hide a hard core of overdue tasks.
Check cumulative risk too, since several minor deferred tasks on one machine may combine into a material reliability problem, and use a risk review for exceptions that records who accepted the temporary delay, what controls apply meanwhile and the new action date. Keep a visible owner for each open deferred job, whether a scheduler, maintenance lead or asset owner, because without ownership backlog reports become storage rather than action.
Measure backlog by age band and criticality, since a count of 50 tells little about whether the oldest high-risk jobs are moving, and investigate recurring causes by changing stocking, ordering or shutdown planning rather than resetting dates. Close a job only after actual work, tests and required records are done; for owners, reschedule backlog shows maintenance debt before it turns into avoidable downtime and makes delayed work and accepted risk visible for decisions.
In practice
Real-world examples.
Example
A required inspection moves twice because production cannot release a machine. The planner keeps the original due date in the record and adds both moves with reasons. By the second move the inspection is a week beyond its original due date, so the asset owner is asked to approve interim controls.
Example
A missing bearing delays a scheduled service and remains visible against its original due date. The store reserves the part when it arrives, and the planner books the first available shutdown. The backlog report shows the job as 11 days late, with the parts delay recorded as the cause.
Example
A low-risk task is moved into a planned shutdown with recorded approval. The cleaning of a conveyor guard is combined with a larger overhaul scheduled for the following week. The move is logged once, the reason is clear and the job closes on the new date.
Formula
Calculation
Reschedule age (days) = current planned date - original due date. Reschedule backlog rate (%) = open preventive jobs with a reschedule / all open preventive jobs x 100. Neither number is proof that an asset was unsafe; they show how much planned work has been pushed back.
Worked example 1: a job first due September 1 and now planned for September 20 has a reschedule age of 19 calendar days, and that is schedule movement, not 19 days of unsafe operation.
Worked example 2: a fictional plant has 40 open preventive jobs, of which 12 carry a reschedule. The backlog rate is 12 / 40 x 100 = 30%. Of the 12, 6 are 7 days or less beyond their original due date, 3 are 8 to 14 days beyond and 3 are 15 days or more beyond, and 5 of the 12 are past the allowed maintenance window, a past-window rate of 5 / 40 x 100 = 12.5%. Two of the three oldest jobs are on safety-critical assets, so the review starts there, even though the total count of 12 looks modest.Case study
Seen in the real world.
This entirely fictional example follows Crest Plastics. Its maintenance board looked current because supervisors changed due dates whenever parts were late. Of 62 open jobs, none appeared overdue. The team added original-due and reschedule-history fields.
The board then showed that 14 jobs were more than two weeks beyond their original due dates, and a safety-critical inspection surfaced as repeatedly deferred, having moved three times. The asset owner reviewed interim controls and scheduled a shutdown, and the stores team changed its reorder points for the parts that caused most delays. The story does not determine legal inspection intervals.
Watch out
Common mistakes.
- Resetting the original due date every time a job moves.
- Treating a reschedule click as a complete risk review.
- Reporting only total backlog without asset criticality and age.
Questions
People also ask.
What belongs in the backlog?
Open preventive jobs meeting the stated reschedule or overdue definition.
Why keep the original due date?
It shows the true elapsed wait despite later schedule edits.
What should be reviewed first?
High-consequence assets and tasks outside allowed maintenance windows.
From the founder's library
Take it further with the book.
Build your financial confidence beyond this definition. Shihan's full-length guide, Accounting Fundamentals, takes the same plain-English approach and turns it into a complete, practical playbook for non-finance managers, business owners and students - with chapter-end quiz answers and presentation slides included.
25% off with code MMHQ25, applied at checkout. Priced in USD - checkout may show the equivalent in your local currency.
View the book and save 25%Related